This invention relates generally to devices for use in lifting and elongated structures lying horizontally on a support structure to a substantially vertical position, and more specifically to such devices for raising and lowering stacks of tires.
In the truck tire retreading business, used truck tires are normally brought into the plant and then are stacked on pallets eight tires high until the tires are ready for processing. Because these tires weigh on the order of 125 pounds each, they are generally too heavy for a single man to lift and place the last few tires on the top of a stack. Thus, it often requires two men to complete each eight-tire stack. After being stacked on a pallet, the tires can then be moved about the plant by a single man using an ordinary forklift truck or forklift cart.
The present method of manually stacking tires on pallets suffers from two distinct drawbacks. First, it is inefficient to require the use of two persons to stack the tires. This inefficiency is even more significant when one realizes that the second person is only needed to stack the last few tires but is not needed to begin the stack of tires or to move the tires around the plant once stacked. Second, when only a single person is available to stack the tires, that person runs the risk of injury due to over exertion in having to stack heavy tires to heights above their chest level.
U.S. Pat. Nos. 5,385,440 and 5,562,392 to Raben disclose several embodiments of tire-stacking devices, tire transporting devices and other accessories, for use in cooperative arrangement with a lift truck. In operation, each of these devices are disclosed as being liftable to a transport position by an ordinary lift truck, whereby these devices and their cargo are supported by the lift truck carriage.
The foregoing arrangement works well in situations where an ordinary lift truck is available for use, where the working space is sufficiently large to permit the lift truck to be maneuvered about, and where maximization of tire stacking density is not of paramount concern. In any of these situations where an ordinary forklift truck cannot be used, however, alternate provisions must be made to effectively stack and transport the tires.
One possible solution is to provide a known forklift cart, such as that shown in FIGS. 57A-57C, for transporting, depositing and retrieving the stacks of tires. Such forklift carts are typically less expensive than forklift trucks, are more maneuverable than forklift trucks, and are typically more capable than forklift trucks of transporting cargo to tight spaces as well as retrieving cargo from densly packed cargo areas. What is needed in such an alternate arrangement, however, is a device for raising a tire stacker, such as any one of the tire stackers disclosed herein, from a horizontal position wherein a plurality of tires can be positioned thereon in side-by-side relation, to a substantially vertical position wherein the plurality of tires become a stack of tires, and for lowering the stacker from its vertical position to its horizontal position. Such a lifting device should preferably be operable to raise the tire stacker to a height sufficient to permit the forks of the forklift cart to freely extend under the stack of tires. In this way, a stack of tires may easily be transferred from the tire stacker to the forklift cart or vice versa. In situations where an ordinary forklift truck cannot be used, this alternate arrangement can therefore be used to enable a single person to stack tires and transport the stack, and further to lower and existing stack to a horizontal tire access position, each in an efficient manner without running the risk of injury due to over exertion.